1. Field
Methods and apparatuses consistent with exemplary embodiments relate to encoding and decoding signals, and more particularly, to processing a signal by which a sound quality deterioration occurring in down-mixing can be reduced.
2. Description of the Related Art
In order to realize a stereophonic and realistic audio system, a multichannel audio device has been developed. In more detail, an audio system, which outputs a plurality of audio channel signals through a plurality of speakers, respectively, e.g., a 2 channel or a 5.1 channel audio system, has come into wide use.
A case where the number of channels is to be reduced to encode multichannel audio signals may occur. For example, a 5.1 channel audio system includes a front left speaker, a front right speaker, a front center speaker, a back left speaker, a back right speaker, and a sub-woofer. The 5.1 channel audio system divides and outputs the multichannel audio signals through the above speakers, respectively. It may be advantageous in some cases for multichannel audio signals including a plurality of audio signals to be encoded by reducing the number of channels. For example, a 5.1 channel signal that is a multichannel audio signal may be output through two speakers. Alternatively, the 5.1 channel signal may be transmitted through 4 audio channels.
If the number of speakers or the number of transmission channels is lower than the number of channels of the audio signal, the number of channels of a multichannel audio signal is to be reduced to encode the multichannel audio signal. Encoding which reduces the number of channels is referred to as down-mixing.
However, if down-mixing is performed, a quantization error and a prediction error may occur when a decoder decodes an encoded audio signal. As a result, a section in which an audio signal is not appropriately restored occurs, and thus sound quality is deteriorated. In more detail, if an audio signal is not appropriately restored, discontinuity of the audio signal occurs in a corresponding section.